Perforated Cigarette Paper

ABSTRACT

The invention relates to cigarette paper ( 1 ) providing self-extinguishing properties to a cigarette made therefrom, wherein the cigarette paper comprises at least one discrete region ( 2 ) that is perforated and comprises a permeability to air that is greater than the permeability to air outside of the perforated region. The perforated region is preferably present in a finished filter cigarette in the vicinity of the filter ( 5 ).

TECHNICAL FIELD

The present invention relates to a cigarette paper that provides acigarette manufactured therefrom with self-extinguishing properties andhas at least one discrete perforated area.

BACKGROUND ART

Due to legal regulations regarding the self-extinguishment ofcigarettes, there is a need within the cigarette industry to providecigarettes which ensure this self-extinguishment. Smoldering cigarettesleft unattended are thus to be prevented from igniting furniture, bedsor other home textiles. It is thus sought to produce cigarettes whichhave a reduced tendency to ignite other materials if the smolderingcigarette comes into contact with these materials.

A test to determine the ignition tendency of cigarettes is described inASTM E2187-04b. The test consists of placing a smoldering cigarette on asubstrate consisting of 10 layers of a filter paper. The test isperformed on 40 cigarettes and the percentage of the cigarettes whichself-extinguish on the substrate before the glowing cone reaches thecigarette filter is determined.

Within the scope of the invention, the self-extinguishing property canbe understood for example to mean that at least the majority of thecigarettes tested according to ASTM E2187-04bfulfill the aforesaidcriterion, that is to say the percentage is above 50%.

A typical cigarette consists of tobacco, which is enwrapped by acigarette paper and together therewith forms a typically cylindricaltobacco rod. The tobacco rod is usually adjoined by the filter, whichconsists typically of cellulose acetate fibers. The filter and thetobacco rod are enwrapped by the tipping paper. The tipping paperconnects the filter to the tobacco rod.

The self-extinguishment of a cigarette is in most cases achieved bycorresponding design of the cigarette paper, that is to say of the paperenwrapping the tobacco. The cigarette paper is designed such that thediffusion constant is so low, at least in some areas of the cigarettepaper, that insufficient oxygen to maintain the smoldering processreaches the glowing cone. As a consequence, the smoldering cigaretteself-extinguishes.

Typical cigarette papers consist of cellulose fibers, obtained fromwood, flax or other materials. Mixtures of cellulose fibers of differentorigin can also be utilized. Cigarette papers have a typical basisweight of 10 g/m² to 60 g/m², wherein the range of 20 g/m² to 35 g/m² isgenerally preferred.

Cigarette papers often also comprise inorganic, mineral fillers, whichare added to the paper in a mass fraction of 10% to 40%. A frequentlyused filler material is chalk (calcium carbonate), but other oxides andcarbonates, such as magnesium oxide and aluminum hydroxide, can also beutilized.

Cigarette paper can also be equipped with burning salts, which increaseor reduce the burn rate of the paper. Sodium citrate and tripotassiumcitrate as well as mixtures thereof are used very frequently and areadded to the paper in an amount of 0% to 5% of the paper mass. The groupof burning salts of technical relevance additionally comprises citrates,malates, tartrates, acetates, nitrates, succinates, fumarates,gluconates, glycolates, lactates, oxalates, salicylates,α-hydroxycaprylates and phosphates, however.

Cigarette papers are typically produced in rolls having a width between0.3 m to 5 m and for example a recut into bobbins having a width,derived from the cigarette circumference, typically of 9 mm to 35 mm.

One possible method to obtain self-extinguishment is to choose acigarette paper of which the diffusion constant is already so low as aresult of the paper production process that the cigarette extinguishesby itself. As a consequence however, the flow of air into the cigarette,that is to say the air permeability, is highly reduced due to a pressuredifference. This has proven to be disadvantageous, since the smoke inthe tobacco rod of the cigarette can only be diluted to a very smallextent by the inflowing air during the smoking process and the cigarettesmoke values for tar, nicotine and especially carbon monoxide areincreased considerably. For example, the air permeability of such papersis less than 10 CORESTA Units (1 CORESTA Unit=1 CU=1 cm³/(cm³ min kPa)),whereas typical cigarette papers, which are not self-extinguishing, havean air permeability between 20 CU and 300 CU.

This disadvantage is eliminated by perforating the cigarette paper overits entire surface. Large holes compared to the natural pore structureare thus created in the paper and increase the air permeability, butcause little change to the diffusion constant of the paper. A dilutingairflow into the cigarette during the smoking process is thus enabledand the cigarette smoke values are lowered without impairing theself-extinguishment of cigarettes manufactured from this paper in theabove-mentioned test.

This perforation can be carried out by different methods. For example,electrostatic perforation is used, in which the paper is transportedthrough one or more spark discharge gaps, which burn holes into thepaper. These holes typically have a diameter between 5 μm and 100 μm.Furthermore, laser perforation can be used, which generates slightlylarger holes having a typical diameter between 50 μm and 500 p.m. Afurther example is mechanical perforation, in which needles or similartools produce holes in the paper. These holes have a typical diameterbetween 100 μm and 2000 μm.

The air permeability achieved with the perforation methods can be veryhigh, for example up to more than 6000 CU, although the cigarette papersare generally perforated such that the air permeability after theperforation is between 50 CU and 500 CU.

The perforation process can be performed after paper production onseparate, dedicated perforation machines in roll or bobbin width. Ofcourse, perforation on the cigarette machine is also possible, that isto say before, during or after the production of cigarettes or similartobacco products from the cigarette paper on the cigarette machine, byany desired perforation method.

Perforation of a cigarette paper over the entire surface thereof, saidcigarette paper having low initial air permeability, has a significantdisadvantage however in the smoker's acceptance of a cigarettemanufactured from this paper. Because of the high air permeability, alot of diluting air flows into the cigarette during the smoking process.The tobacco rod and therefore also the perforated cigarette paper arethen consumed during the smoking process. The area through which thediluting air can flow into the cigarette is thus reduced with every pufftaken by the smoker on the smoldering cigarette as well as during thesmoldering process. This causes the smoker to receive an amount of tar,nicotine and carbon monoxide that increases with each puff as thetobacco rod becomes accordingly shorter. He thus feels that thecigarette is getting “stronger” with each puff. This sensation isundesirable.

One possibility to compensate for this effect is not to choose constantair permeability over the length of the tobacco rod, but instead toprovide a continuous air permeability profile along the cigarette shaftby perforation of the cigarette profile so that during the smokingprocess the increase in the cigarette smoke values with each puff isreduced to the greatest possible extent. A repeated continuous airpermeability profile is therefore to be produced over the cigarettepaper web by perforation.

Although this method is theoretically possible, substantial technicalproblems arise. On the one hand the regulation of the perforation devicefor producing such a continuous profile is very demanding and thecontinuous measurement of the air permeability for the regulation canonly be carried out imprecisely and is not feasible at high speed. Thespeed at which such profiles can be produced, if at all possible, isalso accordingly low.

On the other hand, the endless tobacco rod formed from the cigarettepaper on the cigarette machine has to be cut precisely at the beginningand at the end of such a continuous air permeability profile, so thatthe air permeability profile is in the correct position on the finishedcigarette. The beginning of the profile can only be detected veryimprecisely however, if at all, due to the continuous progression of theair permeability.

The object of the present invention is therefore to overcome thedisadvantages of the prior art.

SUMMARY

The object of the invention is achieved by a cigarette paper thatprovides a cigarette manufactured therefrom with self-extinguishingproperties, wherein the cigarette paper comprises at least a firstdiscrete area, which is perforated and has an air permeability greaterthan the air permeability beyond the first perforated area.

In one embodiment of the cigarette paper, the air permeability withinthe first perforated area is constant over the entire perforated area.

In one embodiment of the cigarette paper, the air permeability withinthe first perforated area is from 50 CU to 2000 CU, preferably from 100CU to 1000 CU.

In one embodiment of the cigarette paper, the width of the firstperforated area is between 2 mm and 25 mm, preferably between 4 mm and12 mm, more preferably between 5 mm and 9 mm.

In one embodiment, the cigarette paper further comprises a short side A,which is intended to face a filter in the finished cigarette, whereinthe first perforated area is located within the third of the cigarettepaper length adjacent to the short side A, preferably within the quarterof the cigarette paper length adjacent to the short side A, and morepreferably within the fifth of the cigarette paper length adjacent tothe short side A.

In one embodiment, the cigarette paper further comprises a short side A,which is intended to face a filter (6) in the finished cigarette,wherein the mean air permeability within the half or third of thecigarette paper length adjacent to the short side A is greater than themean air permeability of the remaining part of the cigarette paper.

In one embodiment, the cigarette paper comprises at least a seconddiscrete area, which is perforated and separated from the firstperforated area by a non-perforated area. In one embodiment of thecigarette paper, the second perforated area is further away from thefirst short side than the first perforated area.

In one embodiment of the cigarette paper, the air permeability withinthe second perforated area is lower than the air permeability within thefirst perforated area.

In one embodiment, the cigarette paper comprises at least one furtherdiscrete area, which is perforated and is separated from the firstperforated area and the second perforated area by at least onenon-perforated area.

In one embodiment of the cigarette paper, the further perforated area islocated further away from the short side A than the first perforatedarea and the second perforated area.

In one embodiment of the cigarette paper, the air permeability withinthe further perforated area is lower than the air permeability withinthe first perforated area and the second perforated area.

In one embodiment of the cigarette paper, the air permeability withinthe second perforated area and/or the further perforated area isconstant over the respective entire perforated area.

In one embodiment of the cigarette paper, the air permeability withinthe second perforated area and/or the further perforated area is from 50CU to 2000 CU, preferably from 100 CU to 1000 CU.

In one embodiment of the cigarette paper, the width of the secondperforated area and/or of the further perforated area is between 2 mm to25 mm, preferably between 4 mm and 12 mm, and more preferably between 5mm and 9 mm.

In one embodiment of the cigarette paper, the air permeability beyond aperforated area is less than 15 CU, preferably less than 10 CU.

In one embodiment, the diffusivity of the cigarette paper (beyond andwithin a perforated area) or the mean diffusivity of the cigarette paperis less than 0.35 cm/s, preferably less than 0.25 cm/s, and morepreferably less than 0.20 cm/s.

In one embodiment, the cigarette paper comprises one or more mineralfillers, selected from the group consisting of carbonates and oxides,preferably from the group consisting of calcium carbonate, aluminumhydroxide and magnesium oxide, and the weight fraction of the one ormore mineral fillers is particularly preferably from 10% to 40%.

In one embodiment, the cigarette paper comprises one or more burningsalts, selected from the group consisting of citrates, malates,tartrates, acetates, nitrates, succinates, fumarates, gluconates,glycolates, lactates, oxalates, salicylates, μ-hydroxycaprylates andphosphates, preferably selected from the group consisting ofsodium-citrate and tripotassiumcitrate, and the content of the one ormore burning salts is particularly preferably up to 5% by weight.

In one embodiment, the cigarette paper has a basis weight of 10 g/m² to60 g/m², preferably of 20 g/m² to 35 g/m².

The object of the present invention is furthermore achieved by a filtercigarette, comprising a cigarette paper according to the presentinvention and furthermore comprising a filter and a tipping paper,wherein the distance between the tipping paper and the first perforatedarea is less than 10 mm, preferably less than 5 mm.

The object of the present invention is furthermore achieved by a methodfor producing a cigarette paper according to the present invention, saidmethod comprising a perforation step to create at least one perforatedarea by electrostatic perforation, laser perforation and/or mechanicalperforation.

In one embodiment of the method, the perforation step is carried out ona cigarette machine or alternatively on a device separate from thecigarette machine.

The object of the present invention is furthermore achieved by the useof a paper (base paper) to produce a cigarette paper according to thepresent invention, preferably by a method according to the presentinvention, wherein the paper is provided in the form of a paper webhaving a width of 0.3 m to 5 m or alternatively of 9 mm to 35 mm.

In one embodiment of the use, the air permeability of the base paper isless than 15 CU, preferably less than 10 CU.

In one embodiment of the use, the base paper has a diffusivity of lessthan 0.35 cm/s, preferably of less than 0.25 cm/s, most preferably ofless than 0.20 cm/s.

In one embodiment of the use, the base paper comprises a mineral fillerselected from the group consisting of carbonates and oxides, preferablyselected from the group consisting of calcium carbonate, aluminumhydroxide and magnesium oxide, and the weight fraction of the one ormore mineral fillers is particularly preferably from 10% to 40%.

In one embodiment of the use, the base paper comprises one or moreburning salts selected from the group consisting of citrates, malates,tartrates, acetates, nitrates, succinates, fumarates, gluconates,glycolates, lactates, oxalates, salicylates, α-hydroxycaprylates andphosphates, preferably selected from the group consisting of sodiumcitrate and tripotassium citrate, and the content of the one or moreburning salts is particularly preferably up to 5% by weight.

In one embodiment of the use, the base paper has a basis weight of 10g/m² to 60 g/m², preferably of 20 g/m² to 35 g/m².

The object of the present invention is furthermore achieved by use of acigarette paper according to the present invention to produce acigarette according the present invention.

The present invention is based on the fact that it has surprisingly beenfound that it is not necessary to produce a continuous air permeabilityprofile but that it is instead sufficient to perforate, over thecigarette paper, a discrete area with constant air permeability arrangedclose to the cigarette filter to achieve a comparably good effect.

If one discrete perforated area close to the filter is insufficient,because the cigarette smoke values are still too high, further discreteareas with different air permeability can of course be produced byperforation and are then located accordingly closer to the end of thecigarette to be lit. Two such discrete perforated areas are oftensufficient.

If two or more discrete perforated areas—viewed in longitudinaldirection of a cigarette to be produced from this paper—are arranged insuccession, there is still preferably a tendency to increase the airpermeability in the direction towards the mouthpiece, that is to say theend opposite the end to be lit. For example, the mean air permeabilityin the half or third of the cigarette paper closer to the mouthpiece ispreferably higher than in the remaining part of the cigarette paper.

Although the cause of this effect is not fully known, the followingexplanation may give an indication as to how it is achieved. During thesmoking process, a negative pressure with respect to the ambient air isproduced at the mouth end of the cigarette to cause an airflow throughthe cigarette and to transport the smoke through the filter to thesmoker. This negative pressure decreases along the cigarette, so thatapproximately no pressure difference exists between the point directlyin front of the glowing cone and the ambient air.

A discrete perforated area located close to the cigarette filter is thensituated in an area of the tobacco rod in which the pressure differencebetween the ambient air and the inside of the tobacco rod is high duringthe smoking process, that is to say a comparably large amount of air canflow into the tobacco rod. In areas closer to the glowing cone andfurther away from the mouth end, this pressure difference is smaller.These areas therefore contribute less to the air volume flowing into thecigarette and there is little influence on the cigarette smoke valuesduring a puff if these areas are not perforated, that is to say have lowair permeability.

Since the perforated areas are discrete in nature and are clearlyseparated from the non-perforated areas, they can be clearly detectedwith optical sensors and it is not difficult to synchronize the paperfeed and the cutting process on the cigarette machine such that thediscrete areas on each cigarette are situated in the desired positionclose to the filter.

Additionally, the air permeability in each of the perforated areas isconstant. Therefore the perforation device just needs to be switched onand off at a frequency corresponding to the speed of the paper web. Thisis much easier than following a continuous air permeability profile.Also, perforation of discrete areas with different air permeability,which is constant within the region however, causes no difficultiessince the perforation power of the perforation device can be adjustedeasily each time said device is switched on or off.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of a cigarette with an exemplaryembodiment of the cigarette paper 1 according to the invention,comprising a first perforated area 2, a second perforated area 3 andfurther perforated areas 4. In this illustration, the cigarette paper 1is partly unrolled from the tobacco column 7 of the cigarette. A filter6 and tipping paper 5 partially enwrapping it as well as a short side Aare also illustrated.

FIG. 2 shows the specific perforation pattern of the cigarette paper toachieve the desired effect. This pattern results from the typicalproduction process of machine-made cigarettes. The perforated areas ofthe wrapper, denoted by numbers, in FIG. 2 correspond to those ofFIG. 1. When producing cigarettes, an endless tobacco rod is firstformed and is then cut along lines B into pieces measuring double thelength of the tobacco rod of a cigarette. In a subsequent step of thecigarette production process, this double-length part of the tobacco rodis cut into two pieces along line C and separated in the axial directionso that a double-length filter tip can be placed in between. The entiredouble-length filter and sub-area of the tobacco rods adjacent to thefilter are adhered and wrapped with a double-width tipping paper. Afterthis, the double cigarette, connected by the double length filter, iscut into two cigarettes by a final cut through the middle of the filter.The pattern to be produced by perforation on the cigarette paper canalso be adapted to other methods of cigarette production.

DETAILED DESCRIPTION Example 1

Starting point of the examples is a cigarette paper having the followingspecification:

Basis weight 28 g/m² Filler fraction 21% of the paper mass Filler chalkBurning salt fraction 1% Burning salt potassium citrate Air permeability6 CU Diffusivity 0.2 cm/s (for CO₂)

The diffusivity is the diffusion constant of the paper [cm²/s] dividedby the thickness of the paper [cm]. It is a transfer coefficient anddescribes the gas flow through the paper at a given concentrationdifference independently of the thickness of the paper. The diffusivitycan be measured for example with a CO₂ diffusivity meter by Sodim.

Of course, equally good results can also be achieved with othercigarette papers, for example with a different basis weight, differentfillers and filler fraction, different burning salts and differentburning salt fraction, as long as the air permeability thereof beforeperforation correspondingly low, that is to say typically less thanapproximately 15 CU, or the diffusion constant thereof is less thanapproximately 0.35 cm/s, to ensure the self-extinguishment of thecigarettes manufactured therefrom.

This cigarette paper was then perforated electrostatically over itsentire surface, so that an air permeability of 50 CU, 100 CU, 150 CU and200 CU was achieved.

Further paper samples were prepared from the same cigarette paper, inwhich discrete areas were perforated instead of the entire surface.These areas were designed as bands, so that the perforated area had adefined width but enclosed the cigarette entirely in the circumferentialdirection. The papers were equipped with one or two bands, althoughthere is no reason why more bands cannot also be provided, however. Thespecifications of these papers are listed in Table 1:

TABLE 1 Specifications of the paper samples Area 1 Area 2 Comparable airDistance* Width Air Permeability Distance* Width Air Permeabilitypermeability ** Sample [mm] [mm] [CU] [mm] [mm] [CU] [CU] A 1 6 160 50 B1 6 650 200 C 1 6 120 30 6 120 50 D 1 6 240 30 6 240 100 E 1 6 370 30 6370 150 F 1 6 500 30 6 500 200 G 3 6 160 50 H 5 6 160 50 J 1 7 140 50 K1 9 110 50 L 1 6 130 30 6 90 50 M 1 6 410 30 6 270 150 N 1 20 90 50 *Thedistance is the gap from the front edge of the tipping paper to thebeginning of the discrete perforated area. ** The comparable airpermeability is the air permeability of the cigarette paper perforatedover its entire surface that provides the same cigarette smoke values onthe test cigarette as the cigarette paper perforated in discrete areas.

Cigarettes with the following specifications were manufactured from allpapers:

Cigarette length 84 mm Filter length 20 mm Length of the tipping paper24 mm Length of the tobacco rod 64 mm Length of visible tobacco rod 60mm Diameter 7.8 mm Tobacco weight 650 mg Tobacco Blend American BlendDegree of filter ventilation 15%These specifications are understood to be merely exemplary, and theinvention can of course be applied to any other cigarette design withcomparable success.

The ignition propensity of all cigarette samples was first testedaccording to ASTM E2187-04b. In accordance with ASTM E2187-04b, 40cigarettes were tested per cigarette paper and 90% or more of the testedcigarettes of all samples self-extinguished, wherein no statisticallysignificant differences between the samples could be found.

The cigarettes were further smoked by the method presented in DIN ISO4387. With this method, a volume of 35 cm³ in 2 seconds is drawn at themouth end of the smoldering cigarette every minute. This drawing of 35cm³ is called a puff. The procedure is repeated until the cigarette issmoked below a minimum length defined by the standard. The smoke isdrawn through a glass fiber filter, which is chemically analyzed lateron. From this, the nicotine-free dry condensate (“tar”) and the nicotineare determined and are usually given in units of mg per cigarette.

The machine smoking was carried out on a smoking machine of theBorgwaldt RM20 type, which was modified however such that every puff ofthe cigarette was passed through a different glass fiber filter, so thatthe cigarette smoke values of each puff could be determined afteranalysis. 20 cigarettes from each paper sample were machine-smoked inthis way.

Since the cigarette is lit at the first puff, the first puff is anexception with respect to its cigarette smoke values and will beexcluded from the considerations. It is also possible during thestandardized, machine smoking that the last puff cannot be fully carriedout, because the cigarette falls below the prescribed minimum lengthduring the puff. Such a puff (“fractional puff”) is recorded as afraction of a whole puff. To simplify the presentation, the last puff istherefore also excluded from the considerations.

Generally, there is a monotone increase of the cigarette smoke valuesfrom puff to puff. To describe the non-uniformity of the cigarette smokevalues from puff to puff the ratio of the nicotine-free condensate(“tar”) between the penultimate puff and the second puff of thecigarette is calculated. This ratio is listed in Table 2. The higherthis ratio, the stronger the cigarette smoke values increase from puffto puff and the more non-uniform is the puff profile.

TABLE 2 Non-uniformity of the cigarette smoke values Penultimate Ratioof Tar: Reduction Sample second puff Comparative Value*** |%| A 1.231.42 −13.4 B 1.65 2.08 −20.7 C 1.25 1.42 −12.0 D 1.36 1.55 −12.2 E 1.531.73 −11.6 F 1.72 2.08 −17.3 G 1.30 1.42 −8.4 H 1.35 1.42 −4.9 J 1.221.42 −14.1 K 1.25 1.42 −12.0 L 1.23 1.42 −13.4 M 1.47 1.73 −15.0 N 1.311.42 −7.7 ***The comparative value is the ratio of tar between thepenultimate and the second puff for a cigarette with a cigarette paperperforated over the entire surface and with the air permeability givenin Table 1.All samples show an improvement in the uniformity of the puff profile,wherein typically a reduction of the observed tar ratios ofapproximately 5% to 20% is achieved.

Example 2 Samples A and B

At first it can be seen that the concentration of the perforation indiscrete areas close to the filter allows a reduction in the airpermeability, since the perforated areas are now located in a region inwhich the difference between the ambient air pressure and the pressurewithin the tobacco rod during the smoking process is higher than inregions located closer to the glowing cone. The paper, which isperforated over the entire surface, has an air permeability of 50 CUover a length of 60 mm, whilst sample A is perforated only over a tenthof this length, namely 6 mm. It would be expected that, to get the sameairflow into the cigarette, the air permeability needs to be 10 times ashigh, that is to say 500 CU. Surprisingly, it can be seen that just 160CU are sufficient to achieve the same cigarette smoke values. Regardingthe uniformity of the puff profile, an improvement in the tar ratio ofapproximately 13% from 1.42 to 1.23 is achieved.

At higher air permeabilities (sample B), this effect becomes even morepronounced. In this case too, an air permeability of 650 CU instead of anominal value of 200×60/6=2000 CU is sufficient.

Example 3 Samples C-F

If the cigarette paper is perforated in two discrete areas instead ofone discrete area, then cigarette smoke values comparable to a cigarettewith a cigarette paper perforated over the entire surface can beachieved with even lower air permeability. This is obvious, since theperforated surface area is now twice as large compared to just oneperforated area. Theoretically, the air permeability of sample C couldbe chosen to be half as much, that is to say 80 CU. However, the secondperforated area is located further away from the mouth end and thereforein a region in which the pressure difference is no longer as high.Moreover, it is consumed during the smoking process. Its contribution istherefore smaller and hence both areas of sample C needed to beperforated with 120 CU to obtain cigarette smoke values comparable tothose of a cigarette with a 50 CU paper perforated over the entiresurface. These considerations apply accordingly at the higher airpermeabilities of samples D, E and F.

With regard to the ratio of the tar values, a distinct improvement ofapproximately 10% to 20% compared to perforation over the entire surfacecan be seen, though this improvement is not as distinct as with just oneperforated area.

Due to the lower air permeability, it is possible to carry outperforation at lower power and higher speed, and therefore thisadvantage has to be weighed against the reduced improvement in theuniformity of the puff profile.

Example 4 Samples A, G and H

The samples A, G and H differ solely in the distance of the perforatedarea from the front edge of the tipping paper. For sample A it is 1 mm,for sample G it is 3 mm, and finally for sample H it is 5 mm. It wasfound that an improvement in the uniformity of the puff profile wasachieved compared to the paper perforated over the entire surface, butthe extent of this improvement decreases quickly if the first perforatedarea is too far away from the front edge of the tipping paper. Morespecifically, the improvement decreases from 13% to approximately 8% at3 mm to just 5% at 5 mm distance. It is therefore preferred to keep thisdistance at least smaller than 10 mm and preferably smaller than 5 mm.

Example 5 Samples A, J, K and N and B

The samples A, J, K and N differ firstly in the width of the perforatedarea. The air permeability was also adjusted accordingly to obtaincomparable cigarette smoke values. Sample A, with a width of 6 mm, has160 CU, sample J, with a width of 7 mm, has approximately 140 CU, andsample K, with a width of 9 mm, has just 110 CU, and sample N, with awidth of 20 mm, lastly has just 80 CU.

An improvement in the uniformity of the puff profile from 7% to 14%could be achieved. This shows that the influence of the width is rathersmall. It may be assumed that the perforated area may also have a widthof more than 20 mm if an improvement is to be achieved. Based on thisdata, the maximum width of the perforated area will be chosen to beapproximately 25 mm.

The minimum width is limited by the maximum air permeability that can beachieved by perforation devices in such a narrow region withoutimpairing the tensile strength of the paper too much. Considering sampleB, with 650 CU over a width of 6 mm as starting point, then a 2 mm widearea must be perforated nominally to 1950 CU to get the same result.This is already a very high air permeability that is difficult toachieve in such a small area, which is why the width of the perforatedarea is to be between 2 mm and 25 mm, preferably between 4 mm and 12 mm,and more preferably between 5 mm and 9 mm.

Example 6 Sample A, E, L and M

Finally, samples L and M show that the air permeability of the twoperforated areas need not be the same. Based on the previous results, itseems to be advantageous to perforate more intensely the area locatedcloser to the mouth end. For samples L and M, the air permeability ofthe first area is approximately 150% of the air permeability of thesecond area.

At approximately 13% (sample L), the achieved improvement in the ratioof the tar values is comparable to a paper with a perforated area fromsample A.

At higher air permeability however, as in samples E and M, it can beseen that, at −11.6%, the use of the same perforation level in bothareas (sample E, 370 CU) provides a result worse than with the unequallyperforated paper from sample M (410 CU/270 CU) with a −15% change in thetar ratio.

In any case, it can be assumed from these results that it is notadvantageous to perforate the second area more intensely than the firstarea. As far as it is technically expedient and reconcilable with thecigarette smoke values, it is sought to perforate the second area lessintensely.

Similarly, for a plurality of perforated areas, it is true that, viewedfrom the mouth end to the glowing cone, each area should be perforatedless intensely than its predecessor.

There is also no reason to provide the areas with different widths.Likewise, the position of the perforated areas can also be varied.

On the whole, many further variations of this invention are conceivableand the examples here merely illustrate the principle of the inventionand are not intended to be limiting.

What is claimed is:
 1. A cigarette paper that provides a cigarettemanufactured therefrom with self-extinguishing properties, wherein thebase paper has a CO₂ diffusivity of less than 0.35 cm/s and thecigarette paper comprises at least one discrete area, wherein this areais perforated and has an air permeability greater than the airpermeability beyond the perforated area.
 2. The cigarette paperaccording to claim 1, wherein the air permeability within the perforatedarea is constant over the entire perforated area.
 3. The cigarette paperaccording to claim 1, wherein the air permeability within the perforatedarea is from 50 CU to 2000 CU.
 4. The cigarette paper according to claim1, wherein the air permeability within the perforated area is from 100CU to 1000 CU.
 5. The cigarette paper according to claim 1, wherein thewidth of the perforated area is between 2 mm and 25 mm.
 6. The cigarettepaper according to claim 1, wherein the width of the perforated isbetween 4 mm and 12 mm.
 7. The cigarette paper according to claim 1,wherein the width of the perforated is between 5 mm and 9 mm.
 8. Thecigarette paper according to claim 1, further comprising a short side Afor facing a filter in the finished cigarette, wherein the perforatedarea is within the third of the cigarette paper length adjacent to theshort side A, preferably within the quarter of the cigarette paperlength adjacent to the short side A, and more preferably within thefifth of the cigarette paper length adjacent to the short side A.
 9. Thecigarette paper according to claim 1, further comprising a short side Afor facing a filter of the finished cigarette, wherein the mean airpermeability within the half or third of the length of the cigarettepaper adjacent to short side A is greater than the mean air permeabilityof the remaining part of the cigarette paper.
 10. The cigarette paperaccording to claim 1, comprising at least a second discrete area that isperforated and separated from the first perforated area by anon-perforated area.
 11. The cigarette paper according to claim 10,further comprising a short side A for facing a filter of the finishedcigarette, wherein the second perforated area is located further awayfrom the short side A than the first perforated area.
 12. The cigarettepaper according to claim 10, wherein the air permeability within thesecond perforated area is lower than the air permeability within thefirst perforated area.
 13. The cigarette paper according to claim 10,comprising at least one further discrete area that is perforated andseparated from the first perforated area and from the second perforatedarea by at least one non-perforated area.
 14. The cigarette paperaccording to claim 13, further comprising a short side A for facing afilter of the finished cigarette, wherein the further perforated area islocated further away from the short side A than the first perforatedarea and the second perforated area.
 15. The cigarette paper accordingto claim 13, wherein the air permeability within the further perforatedarea is lower than the air permeability within the first perforated areaand the second perforated area.
 16. The cigarette paper according toclaim 1, wherein the air permeability beyond a perforated area is lessthan 15 CU.
 17. The cigarette paper according to claim 1, wherein theair permeability beyond a perforated area is less than 10 CU.
 18. Thecigarette paper according to claim 1, having a mean CO2 diffusivity ofless than 0.25 cm/s.
 19. The cigarette paper according to claim 1,having a mean CO2 diffusivity of less than 0.20 cm/s.
 20. A cigarettecomprising a cigarette paper according to claim 1 and furthermorecomprising a filter and a tipping paper, wherein the distance betweenthe tipping paper and the first perforated area is less than 10 mm. 21.The cigarette of claim 20, wherein the distance between the tippingpaper and the first perforated area is less than 5 mm.
 22. A method forproducing a cigarette paper according to claim 1, comprising aperforation step to create at least one perforated area by at least oneof electrostatic perforation, laser perforation, and mechanicalperforation.
 23. The method according to claim 22, wherein theperforation step is carried out on a cigarette machine or on a deviceseparated from the cigarette machine.
 24. Use of a paper to produce acigarette paper according to claim 1, wherein the paper is provided inthe form of a paper web having a width of 0.3 m to 5 m or of 9 mm to 35mm.
 25. Use of a cigarette paper according to claim 1 to produce acigarette according to claim 20.